1. Technical Field
The present invention relates to an image generating device, an image generating method and a printing device.
2. Prior Art
With the evolving high performance of document preparation systems and document printing systems using computers in recent years, there are increasing desires of users for realizing complicated expression in drawing. For example, gradation (gradually changing the color in a prescribed drawing area) is being used a lot for effective presentation, for expressing three-dimensional shapes, etc.
In order to print such a gradation (i.e. an image having gradation) with a printer or display such a gradation on a display, it is necessary to generate a gradation pattern in the bitmap format and draw the gradation pattern on a page memory or frame memory. The drawing of the gradation is carried out by successively drawing (overlaying) multiple areas slightly differing in the color value while gradually shifting the drawing position of each area. The drawing of such a gradation requires complicated calculations since each of such areas (to be drawn with the same (uniform) color value) has to be determined and specified for the drawing.
Under such circumstances, various devices have been proposed in order to draw a gradation while reducing the load related to the drawing of the gradation. For example, an image formation device (capable of drawing a concentric circular gradation) described in Japanese Patent Provisional Publication No. HEI 11-31231 (hereinafter referred to as a “patent document #1”) reduces the load for the gradation drawing by carrying out the gradation drawing by first determining color changing points (at each of which the color value changes) for each scan line and then drawing each line segment between two color changing points (on a scan line) with a uniform color value.
Meanwhile, the XML Paper Specification (hereinafter referred to simply as “XPS”) has recently been established as a PDL (Page Description Language) for describing electronic documents, and a lot of products supporting XPS are being put on the market. In XPS, a RadialGradientBrush element can be described in a document as an image drawing instruction for drawing an elliptical radial gradation, by which more complicated gradational expression is made possible.